Autonomous temperature sensor for bake plate calibration SFR Workshop November 8, 1999 Michiel Krüger, Darin Fisher, Andy Gleckman, Scott Eitapence Berkeley, CA In this project we investigate the feasibility of wireless, autonomous sensors, riding on dummy wafers to measure the temperature distribution across a wafer during semiconductor processing. Off-the-shelf components are used to test the concept. 2/17/2019

Motivation Why autonomous smart dummy wafers? Why temperature? spatial distribution of process variables over area and time real-time wafer-state information useful for: Process design / modeling / control Equipment design / diagnosis Why temperature? Temperature information can be used for feedback control during photo resist baking and plasma etching. DUV photo resist is very sensitive to bake process: temperature transient info can be used to: calibrate detailed DUV photo resist models accurately determine overall thermal budget of photo resist 2/17/2019

Temperature sensor Technology set Features surface mount components minimal processing of host wafer on-board microprocessor with integrated 4 channel A/D off-the-shelf battery technology infrared data transfer (IrDA compliant) with error detection (CRC) Features Distributed array of temperature sensors (0.5 °C resolution) real-time data acquisition wireless power & data transfer PalmPilot interoperability Sensor P Ir-LED Batteries Voltage regulator 2/17/2019

PalmPilot Interface 2/17/2019

Experimental setup Computer controlled bake-plate used for calibration and validation of measurements. Probes used for external powering / measuring. Data from wafer stored on computer via Ir-receiver. Data transmitted at 2Hz. Tethered and untethered. Tests conducted: repeatability (hrs.) fast transients (min.) power consumption (sec.) Wafer Ir-receiver Probes Bake-plate 2/17/2019

Results: tethered power, untethered communication Repeatability test up to 120 °C; externally powered Average current  1mA, current spikes due to data transmission via Ir-LED 2/17/2019

Results: totally autonomous run Button cell/UCLA batteries used for power supply Good result up to 140 °C. Slow and fast transients measured. 2/17/2019

Milestones Year 1 Demonstrate untethered temperature measurements in plasma. (in progress) Year 2 Demonstrate un-tethered real-time temperature and etch rate measurements with integrated power and data processing in plasma. (in progress) 2/17/2019

Future work (2000-2002) Integrate thick film UCLA batteries in current sensor design RF isolation of sensors for use in plasma chamber Low profile temperature sensors (flip-chip components) Total enclosure of components Close the control loop Include other sensors in design (etch rate / stress / ion density) Thermal isolation of electronics / high temp ASIC for operation up to 160 °C battery sensor 2/17/2019